THIS invention relates to abrasive tools.
Abrasive tools are known that comprise a body in which are mounted inserts which have a wear-resistant or abrasive layer. It is this layer that is used to perform a cutting or abrading action. The support for the wear-resistant layer may be in the form of a post of squat proportions. It is the mounting of the post in the working face of the tool body that can present problems to the manufacturer and the user. Until now, such posts have been secured to the body by providing a suitable complementally shaped recess or socket in the working face, locating the post therein and brazing the post to the sides of the socket or recess by means of a suitable braze alloy. Most commonly, the post and the recess are cylindrical.
A disadvantage of this method is that residual stresses are induced at the circumferential region of the post at the area where maximum bending stresses also arise in use. These stresses are of the same order of magnitude as the strength of the braze alloy.
Another disadvantage is that the high temperatures required in the brazing cycle tend to cause deterioration of the post, which is usually made of a carbide, and also of the abrasive layer. This is especially so when the abrasive layer is composed of a diamond composite that is not thermally stable.
It may also happen that the impacts to which the tool are subjected in use may cause sufficient rise in temperature to lead to melting of the braze and consequent failure of the bond.
Another method has been to shrink fit the post so that it is mechanically held in the recess or socket. The socket may be suitably tapered with its cross section decreasing with increasing depth into the body.